A structural system and design method for a long-span, upper-bearing steel truss arch bridge

Abstract

This invention relates to a structural system and design method for a long-span, upper-bearing steel truss arch bridge. The method includes arranging beams of equal span in the mid-span region. When the span-to-pier height ratio (li / hi) is between 0.9 and 1.1, variable-span beam arrangement begins, with the main beam span gradually increasing from the mid-span towards both banks. The main beam is configured as a first, second, and third span arranged sequentially. The second span connects two or three spans in the mid-span, while the first and third spans connect all remaining spans. The main beam is connected to the columns via elastic supports with bidirectional shear deformation capability. This invention effectively coordinates the stress on the beam and arch, effectively reduces the stress on the main beam, significantly improves the overall structural stability, ensures structural safety and reliability, and demonstrates significant economic benefits.

Description

Technical Field

[0001] This invention relates to the field of bridge technology, and in particular to a structural system and design method for a long-span, upper-bearing steel truss arch bridge. Background Technology

[0002] Generally, the lateral deformation of a small-span, upper-bearing steel truss arch bridge is small under crosswinds, the beam-arch lateral bending effect is not obvious, and the lateral force on the structure is small. Therefore, the longitudinal force controls the structural design. To improve the longitudinal stability of the structure, the main beam on the arch is usually set as a single unit, and fixed supports are set between the piers and beams to form a frame to enhance the mutual constraint between the three.

[0003] However, as the span (100 meters and above) increases, the transverse bending deformation of the beam arch caused by the transverse wind increases. At the same time, the proportion of the internal force caused by the transverse wind in the internal force of the arch ring gradually increases. After the span reaches a certain value, the proportion of the internal force caused by the transverse wind is greater than that of the vehicle load. At this time, the structure evolves into a transverse force-controlled structural design.

[0004] If traditional design methods are used for long-span, upper-bearing steel truss arch bridges, the lateral bending deformation of the beam and arch will not be compatible under the action of lateral extreme wind. Excessive beam and arch constraints will cause the main beam to generate a large amount of secondary internal forces, resulting in unreasonable stress distribution. Furthermore, a large number of steel bars or steel strands need to be added to the main beam to meet the stress requirements, which is uneconomical. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a novel large-span upper-bearing steel truss arch bridge structural system and design method, which can effectively coordinate the stress on the beam and arch, effectively reduce the stress on the main beam, effectively improve the stability of the structure, ensure structural safety and reliability, and achieve significant economic benefits.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a design method for a long-span, upper-bearing steel truss arch bridge structural system, comprising the following steps:

[0008] S1. Equal span beams are arranged in the mid-span area. When the equal span arrangement reaches the ratio of span to pier height li / hi between 0.9 and 1.1, variable span beams are arranged. When viewed from the mid-span to both banks, the span of the main beam gradually increases.

[0009] S2. The main beam is configured as a first span, a second span, and a third span arranged in sequence. The second span connects two or three spans in the middle of the span, and the first and third spans connect all the remaining spans.

[0010] S3. The main beam and the column are connected by elastic supports, which have the ability to undergo bidirectional shear deformation.

[0011] The design method of this invention for a novel large-span upper-bearing steel truss arch bridge structure system adopts an equal-span arrangement in the mid-span area to reduce the types of main beams, and a variable-span arrangement on both banks to reduce the number and density of columns. Compared with the equal-span beam arrangement scheme for the entire bridge, this method has stronger structural stability, better economy, and a more aesthetically pleasing appearance. The main beam is divided into three sections, with two or three spans in the mid-span forming one section, which can significantly reduce the transverse bending stress of the main beam and has a smaller impact on the overall structural stability. The internal force is about 1 / 4 of the internal force set for one section of the main beam, which greatly reduces the stress on the main beam and saves material usage. The use of elastic supports with bidirectional shear deformation capability can adapt to the radial force requirements of the supports when the beam arch is transversely bent, which can effectively coordinate the beam arch stress and reduce the secondary internal forces caused by the fan-shaped deformation of the main beam. This design method is simple in steps, easy to operate, and has good results.

[0012] As a preferred technical solution of the present invention, before step S1, the mid-span truss height h is determined based on the span L of the arch ring. For a steel truss arch, the ratio of the mid-span truss height to the span, h / L, is 1 / 45 to 1 / 15, and the value is smaller for the larger the span.

[0013] As a preferred technical solution of the present invention, before step S1, the truss section length d is determined based on the horizontal included angle of the diagonal web members being 45° to 55°.

[0014] As a preferred technical solution of the present invention, in step S1, beams of equal span are laid out between the two quarter points of the span L located on both sides, and the span outside the two quarter points gradually increases towards the shore.

[0015] As a further preferred technical solution of the present invention, the spans on both sides of the quarter points are equal.

[0016] As a preferred technical solution of the present invention, in step S2, if a pier is set at the top of the arch, the two spans in the middle are taken as the second joint; if there is no pier at the top of the arch, the three spans in the middle are taken as the second joint.

[0017] As a preferred technical solution of the present invention, in step S3, the elastic support is provided with longitudinal and transverse limiting blocks.

[0018] As a preferred technical solution of the present invention, in step S3, a longitudinal stop is provided at the bottom of the main beam, and the elastic support has a pad stone, with the longitudinal stop and the pad stone forming a limiting pair.

[0019] Secondly, the present invention also provides a large-span upper-bearing steel truss arch bridge structural system, which is designed using the design method of the novel large-span upper-bearing steel truss arch bridge structural system as described in any of the above claims. The novel large-span upper-bearing steel truss arch bridge structural system includes a main beam, an arch rib, and several columns.

[0020] The columns are connected above the arch ribs, and the main beams are supported on the arch ribs through the columns. The columns in the mid-span area are arranged with equal spans, while the columns on both banks are arranged with varying spans. The span gradually increases from the mid-span to both banks. The main beams include the first span, the second span, and the third span, which are set in sequence. The second span connects the two or three spans in the mid-span, and the first and third spans connect all the remaining spans. The main beams and columns are connected by elastic supports.

[0021] The large-span, upper-bearing steel truss arch bridge structure system described in this invention employs an equal-span arrangement in the mid-span region to reduce the types of main beams, and a variable-span arrangement on both banks to reduce the number and density of columns. Compared with the equal-span beam arrangement throughout the entire bridge, this system offers stronger structural stability, better economy, and a more aesthetically pleasing appearance. The main beam is divided into three sections, with two or three spans in the mid-span forming one section, which significantly reduces the lateral bending stress on the main beam while having a minimal impact on the overall structural stability. The internal forces are approximately one-quarter of those set for a single section of the main beam, greatly reducing the stress on the main beam and saving material usage. The use of elastic supports with bidirectional shear deformation capability can adapt to the radial force requirements of the supports during the lateral bending of the beam arch, effectively coordinating the beam arch stress and reducing the secondary internal forces caused by the fan-shaped deformation of the main beam. This system has a simple structure, is easy to construct, and achieves excellent results.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] The structural system and design method of a long-span upper-bearing steel truss arch bridge described in this invention can effectively coordinate the stress on the beams and arches, effectively reduce the stress on the main beams, significantly improve the overall stability of the structure, ensure structural safety and reliability, and have significant economic benefits. Attached Figure Description

[0024] Figure 1 A schematic diagram of the elevation layout of the main truss with arch ribs;

[0025] Figure 2 This is a schematic diagram of the equal span arrangement in the mid-span area and the variable span arrangement in the two banks area of ​​the main beam in Example 1;

[0026] Figure 3 This is a schematic diagram of the existing technology for equal-span main beam arrangement;

[0027] Figure 4 A schematic diagram of the axial force of the main beam under lateral wind when the main beam is installed in a single unit.

[0028] Figure 5 A schematic diagram of the axial force of the main beam under lateral wind when the main beam is set in a triple configuration;

[0029] Figure 6 A schematic diagram of the fan-shaped deformation of the main beam;

[0030] Figure 7A schematic diagram of the axial force of the main beam under lateral wind when the main beam is a triple span with fixed supports;

[0031] Figure 8 A schematic diagram of the axial force of the main beam under lateral wind when the main beam is a triple span with elastic supports;

[0032] Figure 9 This is a schematic diagram of the arch beams connected by mutual adaptation deformation based on the beams and arches. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings.

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Example 1

[0036] like Figures 1 to 9 As shown, the design method of a novel large-span upper-bearing steel truss arch bridge structural system of the present invention includes the following steps:

[0037] Step 1: Span layout method based on economy, stability, and ease of construction.

[0038] This method employs a beam arrangement with equal spans in the mid-span region and variable spans in the riverbank regions, specifically including:

[0039] First, calculate the span L based on the arch ring to determine the mid-span truss height h. For steel truss arches, the ratio of the mid-span truss height to the span, h / L, is generally 1 / 45 to 1 / 15. The larger the span, the smaller the value.

[0040] Based on the principle that the horizontal included angle of the diagonal web members is 45° to 55°, the truss section length d is determined, and the elevation layout of the main truss of the arch rib is drawn as follows: Figure 1 As shown.

[0041] According to the elevation layout of the main truss of the arch rib, the spans are arranged from the mid-span towards both banks; the span of the main beam is taken as nd, where n is an integer. Since the columns in the mid-span area are relatively short, an equal-span arrangement is adopted to reduce the number of main beam types; when the equal-span arrangement reaches a span-to-pier height ratio li / hi between 0.9 and 1.1, a variable-span arrangement begins, such as... Figure 2 As shown, looking from the mid-span towards both banks, the span of the main beam gradually increases, and the height of the piers also gradually increases, which is visually appealing. At the same time, compared with the equal-span beam arrangement scheme for the entire bridge, the unequal-span beam arrangement scheme has smaller side pier heights, stronger structural stability, and better economic efficiency.

[0042] To better compare the differences between this embodiment and the prior art, and to compare the mechanical properties and material usage of the two solutions, the prior art's slab arrangement method is as follows: Figure 3 As shown, the main beams are arranged with equal spans (hereinafter referred to as Scheme 1). The span arrangement in this embodiment is as follows: Figure 2 As shown, the main beam is arranged with equal spans in the mid-span area and with varying spans on both banks (hereinafter referred to as Scheme 2). Scheme 1 has two more columns than Scheme 2. The total steel consumption of Scheme 1 is 500t more than that of Scheme 2. The structural stability coefficient of Scheme 1 is 0.87 times that of Scheme 2. Scheme 2 is more stable. In summary, Scheme 2 is more economical, more stable, and more aesthetically pleasing.

[0043] Step 2: A method for separating beams and arches based on their mutual adaptive deformation.

[0044] The arch beams are designed in a split configuration to mitigate the axial force effect caused by the fan-shaped bending of the main beam due to the transverse bending of the arch beam under extreme lateral wind conditions. Specifically, this includes:

[0045] The joints are set according to the curvature of the main beam under crosswind. In the mid-span region where the curvature is large, the joint length can be shortened to reduce the axial force effect of the fan-shaped deformation of the main beam. In the sections with smaller curvature at both ends, the joint length can be lengthened to improve the stability of the structure.

[0046] Typically, the main beam of the arch can be divided into three sections, with the side sections being longer and the middle section shorter. The length of the middle section can be determined by taking two spans in the middle of the arch when there is a pier at the top of the arch, and three spans in the middle of the arch when there is no pier at the top of the arch. This division into sections can significantly reduce the lateral bending stress on the main beam, while having a smaller impact on the overall stability of the structure.

[0047] A comparative study of the main girder spans was conducted using the bridge software Midas Civil, comparing the stress conditions of main girders with a single span and those with a triple span configuration. The calculation results are as follows:

[0048] The axial force of the main beam under transverse wind action is as follows: (The main beam is installed in a single span.) Figure 4 As shown;

[0049] The axial force of the main beam under lateral wind action is as follows: (The main beam is configured in three sections) Figure 5 As shown.

[0050] Table 1: Influence of the branch connection on the internal forces of the main beam

[0051] Main beam 1 span 4647～4907 7469～7945 The main beam is divided into 3 sections. 1174～1208 2516～2572

[0052] pass Figure 4 , Figure 5 Table 1 shows that the splitting of the main beam has a significant impact on the stress of the main beam. After splitting into three sections, the internal force of the main beam is about 1 / 4 of the internal force set for a single section of the main beam, which greatly reduces the stress on the main beam and saves material usage.

[0053] Ultimately, the main beam bends laterally under crosswinds, exhibiting a fan-shaped deformation (such as...). Figure 6 As shown in the figure, the outer beam is elongated while the inner beam is shortened. The longer the beam is, the greater the secondary internal force caused by the fan-shaped effect. If the beam is divided into 3 segments, the fan-shaped effect can be effectively released and the stress on the beam can be reduced.

[0054] Step 3: The method for setting up a support system with elastic supports and multiple constraints based on deformation characteristics.

[0055] The supports are elastic supports with bidirectional shear deformation capabilities, which can adapt to the radial force requirements of the supports when the beam arch is bent. This can effectively coordinate the force on the beam arch and reduce the secondary internal forces caused by the fan-shaped deformation of the main beam.

[0056] The support body should be equipped with longitudinal and transverse limiting blocks to ensure that the beam and pier can still effectively restrain each other to maintain the designed structural system after the support shear unit fails. The position of the limiting blocks on the support body should be determined according to the principle that the support shear unit should just hit the block after the maximum deformation.

[0057] In addition to the limiting blocks on the support body, a longitudinal block is set at the bottom of the beam, which together with the support pad stone forms a limiting pair. The distance between the beam bottom block and the support pad stone is determined according to the principle that the beam bottom block just collides with the pad stone when the support shear unit undergoes maximum deformation.

[0058] This embodiment uses a support system with elastic supports and multiple constraints to accommodate the radial deformation of the piers and beams while limiting excessive deformation between them. This system can coordinate the stress on the beam arch, reduce the secondary internal forces of the main beam, and ensure the safety of the structure through multiple lines of defense.

[0059] A comparative study was conducted on the main beam using fixed supports and elastic supports using the bridge software Midas Civil. The calculation results are as follows:

[0060] The main beam is divided into three sections and fixed supports are used. Under the action of lateral wind, the axial force of the main beam is as follows: Figure 7 As shown;

[0061] The main beam is divided into three sections and then supported by elastic supports. The axial force of the main beam under lateral wind action is as follows: Figure 8 As shown.

[0062] Table 2: Influence of Supports on Internal Forces of Main Beam

[0063] The main beam is divided into three sections and uses fixed supports. 2881～3066 5101～6027 The main beam is divided into three sections and uses elastic supports. 1174～1208 2516～2572

[0064] pass Figure 7 , Figure 8 As shown in Table 2, the supports have a significant impact on the stress of the main beam. The internal force of the main beam with elastic supports is about 0.42 times that of the main beam with fixed supports, which greatly reduces the stress on the main beam and saves material usage.

[0065] Ultimately, the main beam bends laterally under crosswinds, exhibiting a fan-shaped deformation (such as...). Figure 6 As shown in the figure, the outer beams extend while the inner beams shorten. Fixed supports restrict the elongation and shortening of the main beams, resulting in larger secondary internal forces. In contrast, elastic supports can adapt to deformation, thus reducing internal forces.

[0066] Figure 9 This diagram illustrates the segmented design of the main beam on an arch. Typically, when the main beam is longitudinally continuous, its deformation under lateral wind action exhibits a semi-sine wave curve. The curvature of both the lateral displacement and deformation curves shows a pattern of larger curvature at the mid-span and smaller curvature at both ends. Segmenting the beam into sections with larger curvature at the mid-span can effectively reduce the lateral stress on the main beam. Generally, the main beam on an arch can be divided into three sections: the side sections are longer, and the middle section is shorter. The length of the middle section can be determined by taking two spans from the mid-span when columns are installed at the arch crown, and three spans from the mid-span when there are no columns at the arch crown. This segmentation significantly reduces the lateral bending stress on the main beam while having a smaller impact on the overall structural stability.

[0067] In one specific implementation, such as Figure 9 As shown, the spans between the two quarter points along the length of the arch rib are equal, and the spans outside the quarter points gradually increase towards the shore. The spans on the adjacent sides of the quarter points are equal. Since no columns are set in the middle of the span, a main beam is set in the middle three spans, and a main beam is set in each of the spans on both sides, forming a three-span main beam.

[0068] The design method of the novel large-span upper-bearing steel truss arch bridge structure system described in this embodiment can effectively coordinate the stress on the beam and arch, effectively reduce the stress on the main beam, significantly improve the overall stability of the structure, ensure structural safety and reliability, and have significant economic benefits.

[0069] Example 2

[0070] like Figure 9 As shown, the present invention discloses a novel large-span upper-bearing steel truss arch bridge structure system, which is designed using the design method of a novel large-span upper-bearing steel truss arch bridge structure system as described in Example 1. The novel large-span upper-bearing steel truss arch bridge structure system includes a main beam, an arch rib, and several columns. The columns are connected above the arch rib, and the main beam is supported on the arch rib through the columns.

[0071] The columns in the mid-span area are arranged with equal spans. When the ratio of span to pier height (li / hi) is between 0.9 and 1.1, a variable span arrangement begins, such as... Figure 2 As shown, the span gradually increases when viewed from the middle of the span towards both banks.

[0072] The main beam includes a first span, a second span, and a third span arranged sequentially. The second span connects two or three spans in the middle of the span, and the first and third spans connect all the remaining spans. Figure 9 As shown, the spans corresponding to the first and third sections have both equal and unequal span arrangements, while the spans corresponding to the second section are arranged with equal spans.

[0073] The main beam and the column are connected by an elastic support. The body of the elastic support includes longitudinal and transverse limiting blocks. The bottom of the main beam is provided with a longitudinal block, which together with the pad stone of the elastic support forms a limiting pair.

[0074] The novel large-span upper-bearing steel truss arch bridge structure system described in this embodiment can effectively coordinate the stress on the beams and arches, effectively reduce the stress on the main beams, significantly improve the overall stability of the structure, ensure structural safety and reliability, and have significant economic benefits.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method for a large-span, upper-bearing steel truss arch bridge structural system, characterized in that, Includes the following steps: S1. Equal span beams are arranged in the mid-span area. When the equal span arrangement reaches the ratio of span to pier height li / hi between 0.9 and 1.1, variable span beams are arranged. Looking from the mid-span to both banks, the span of the main beam gradually increases. S2. The main beam is configured as a first span, a second span, and a third span arranged in sequence. The second span connects two or three spans in the middle of the span, and the first and third spans connect all the remaining spans. The joints are set according to the curvature of the main beam under crosswind. The joint length is shortened in the mid-span area where the curvature is large in order to reduce the axial force effect of the fan-shaped deformation of the main beam. The joint length is lengthened in the sections with smaller curvature at both ends to improve the stability of the structure. S3. The main beam and the column are connected by elastic supports, which have the ability to undergo bidirectional shear deformation.

2. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 1, characterized in that, Before step S1, the mid-span truss height h is determined based on the span L of the arch ring. For a steel truss arch, the ratio of the mid-span truss height to the span, h / L, is 1 / 45 to 1 / 15. The larger the span, the smaller the value.

3. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 1, characterized in that, Before step S1, determine the truss section length d based on the horizontal included angle of the diagonal web members being 45°~55°.

4. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 1, characterized in that, In step S1, beams of equal span are laid out between the two quarter points of the span L located on both sides, and the span outside the two quarter points gradually increases towards the shore.

5. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 4, characterized in that, The spans on either side of the quarter point are equal.

6. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 1, characterized in that, In step S2, if a pier is set at the top of the arch, the two spans in the middle are taken as the second joint; if there is no pier at the top of the arch, the three spans in the middle are taken as the second joint.

7. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to claim 1, characterized in that, In step S3, the elastic support is provided with longitudinal and transverse limiting blocks.

8. The design method for a large-span, upper-bearing steel truss arch bridge structural system according to any one of claims 1-7, characterized in that, In step S3, a longitudinal stop is provided at the bottom of the main beam, and the elastic support has a pad stone. The longitudinal stop and the pad stone form a limiting pair.

9. A large-span, upper-bearing steel truss arch bridge structural system, characterized in that, The design is carried out using the design method of the large-span upper-bearing steel truss arch bridge structure system as described in any one of claims 1-8. The large-span upper-bearing steel truss arch bridge structure system includes a main beam, an arch rib, and several columns. The columns are connected above the arch ribs, and the main beams are supported on the arch ribs through the columns. The columns in the mid-span area are arranged with equal spans, while the columns on both banks are arranged with varying spans. The span gradually increases from the mid-span to both banks. The main beams include the first span, the second span, and the third span, which are set in sequence. The second span connects the two or three spans in the mid-span, and the first and third spans connect all the remaining spans. The main beams and columns are connected by elastic supports.

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